This was done by previous owner and I'm not an expert on stucco repair. They had some nails and other random stuff, stuffed in the holes to try and keep the anchors in to no avail. The holes are now about 3/8" or larger in the stucco. What is the proper way to get this thing anchored and sealed as you can see there is also about a 2" X 4" sized hole for the cables as well.

It should have been mounted using Tap Con screws in predrilled holes.
I'd just use stucco mix to fill in the old holes and redrill new ones for the right sized screws with a hammer drill and a masonery bit.

It should have been mounted using Tap Con screws in predrilled holes.
I'd just use stucco mix to fill in the old holes and redrill new ones for the right sized screws with a hammer drill and a masonery bit.

No, it looks like they tried to use plastic push style drywall anchors the first time around.